The submitter might have been triggered to look the topic up on Wikipedia by the most recent (Aug 10, 2015) installment on Ben Krasnow's Applied Science videos:

The submitter might have been triggered to look the topic up on Wikipedia by the most recent (Aug 10, 2015) installment on Ben Krasnow's Applied Science videos: Learn how magneto-optical storage discs work, and see how a focused laser can directly alter a material's optical characteristics. https://www.youtube.com/watch?v=UTquUbvzJII https://www.youtube.com/watch?v=UTquUbvzJII This video uses a magneto-optical disk as an example material, but there also the material is heated up above the curie point to allow the bit-domains to swap orientation. Readout is optical, though. (hence the name)